Help my puppy is being aggresive to my other puppy!?

I had my puppy Mayuri before my other puppy Lulu. Mayuri is 6 months. Lulu is 4 months. I found Lulu in the streets took her to the vet and took her in my house. They got along just great my first puppy Mayuri was not jealous, my new puppy Lulu was the jealous. But other than that they were fine together. And living together for 2 months. This past week though, Lulu has been SO agressive to Mayuri. Mayuri is just kind of calm and becomes afraid of Lulu. Lulu bites Mayuri and growls at her, mayuri gets afraid and jumps onto me. Lulu is always being aggresive when we hold her she growls at us but rarely bites. How can i stop her behavior? Also can Mayuri die from being scared or something?